My favorite when I was growing was always Watership Down. It was also the first book to really scare me (the warren of wires part still gives me goosebumps!). I loved this book so much, I read it once a year starting in sixth grade all the way up through high school, and I highly recommend it to anyone who's looking for a good non-fantasy adventure story. :)

The movie was a little bit beyond me though ^^;

Enough said.